Handbook of Solvents - George Wypych - ChemTech - Ventech!

1056 George Wypych
except water which is in liquid state) and net heat of combustion (the same but water is also
in a gaseous state). These determinations are useful in assessing the thermal efficiency of
equipment used for generation of power or heat. The results are used to estimate the range of
an aircraft between refueling stops which is a direct function of heat of combustion. The
calorimeter bomb is standardized against benzoic acid standard. Net and gross heats of
combustion are reported. A specific method is used for aviation fuels. 17 This method reports
results in SI units and the measurements are made under constant pressure. The method is
applicable for aviation gasolines or aircraft turbine and jet engine fuels. The method is used
when heat of combustion data are not available. An empirical equation was developed
which gives net heat of combustion based on the determined values of aniline point (ASTM
D 611) and API gravity (ASTM D 287). If the fuel contains sulfur, a correction is applied for
sulfur determined according to ASTM D129, D 1266, D 2622, or D 3120 (the method selected
depends on the volatility of the sample).
Gross calorific value and ash content of waste materials can be determined by a calorimetric
method. 19 After a calorimetric analysis, the bomb washing can be used to determine
of mineral content by elemental analysis. The sample is burned under controlled conditions
in oxygen. The calorimeter is standardized by burning known amount of benzoic acid. The
formation of acids can additionally be determined by titration.
15.1.7 CLEANING SOLVENTS
Several standard procedures are available for evaluation of cleaning solvents. The stability
of aircraft cleaning compounds is determined after 12 months storage at controlled
conditions which may include moderate temperatures, cold storage, and hot storage. 20 Solvent
vapor degreasing operations which use halogenated solvents follow standardized
procedure. 21 The standard contains information on the location and design of a degreasing
installation and operation during startup, degreasing, shutdown, and solvent reclamation.
The purpose of the standard is to reduce the probability of accidents and exposure to
personnel. A separate standard practice 22 gives reasons for and methods of preventing acid
formation in degreasing solvents. The formation of acid is generally related to excessive
heat, contaminations, the presence of chlorinated and sulfonated oils, admixture of acids,
and solvent mixtures.
15.1.8 COLOR
Impurities in benzene, toluene, xylene, naphthas, and industrial aromatic hydrocarbons are
determined by a simple colorimetric analysis of an acid wash. 23 A solvent is washed with
sulfuric acid and the color of the acid layer is determined by a visual comparison with color
standards prepared from solutions of cobalt chloride and ferric chloride.
Aromatic hydrocarbons which melt below 150 o C can be subjected to color analysis in
the liquid (molten) state using a visual comparison with platinum-cobalt standards. 24 Standards
are prepared from a stock solution of K2PtCl2 to form a scale varying in color intensity.
Similar procedure was developed to evaluate color of halogenated organic solvents and
their admixtures. 25
Objective color measurement is based on tristimulus colorimetry. 26 This instrumental
method measures tristimulus values of light transmitted by a sample and compares the results
to the values transmitted by distilled water. The results can be recalculated to the platinum-cobalt
scale referred to in the previous standards. 24,25 The results can also be
interpreted by normal methods of color measurement to yellowness index, color, color
depth, etc.